Tuesday, March 29, 2016

Why give Benadryl to a dog with a mast cell tumor?

Sinead the Boston terrier looking sleepy
Sinead the Boston terrier is very nearly done with her mast cell tumor treatments. But she doesn't look too happy about the whole thing. In fact, she looks downright exhausted. And there's good reason for that. Twice per day, she's taking in a tiny sliver of Benadryl with her dog food. And that drug could be a key weapon in her cancer recovery.

Benadryl is, as you probably know, an antihistamine medication. Humans and dogs use this drug to help them deal with seasonal allergy problems, like sneezing and wheezing and itching. The drug works to calm down the body's histamine response. And it's that histamine that is responsible for most of the misery people feel during the allergy season.

That histamine response is also part of the mast cell tumor process.

A mast cell tumor is made up of tiny cells that play a key role in releasing histamine. They clump together in one big batch, instead of working as independent entities throughout the body, and that little clump is the tumor.

Surgery involves cutting out that clump, and Sinead's electrochemotherapy appointment helped to kill off any remaining cells. That means her tumor is pretty much gone. In fact, you can't even see it anymore.

Sinead the Boston terrier falling asleep

But she might still have rogue little mast cells in the area. Benadryl helps to keep those cells in check. And that could keep them from re-clumping and forming a new tumor in that old and bad spot.

Sinead needs to take Benadryl for another week. That will mean she's been on this therapy for about 2 weeks after her chemotherapy appointment ended. That's a pretty common treatment protocol. Most veterinary teams advise people to use the medication for about 2 weeks after medical appointments, just to help the area stay clean.

But Benadryl can also be a great medication to give before surgery. Why? Because a clump of mast cells can be really dangerous. If they all release histamine at once--which they might want to do if they are poked during a biopsy or a surgery--it can cause a body-wide reaction. That reaction could involve bleeding, swelling or seizing. Using Benadryl before these procedures can ensure that the clump stays silent. And that could mean the difference between a procedure that is safe and one that is a little dangerous.

Anyway. For another week, Sinead will be soft and sleepy like this. Benadryl can do wonders, but it can be super sedating. But when that week is out, she'll be back to her old Boston self. Cancer free, this time.


  1. Thanks for posting this - I'm a CVT and I remember learning this about mast cell tumors. So does Sinead only have one more appointment left in the chemo treatments? I'm sending many positive thoughts and appreciate you sharing all of this as you go through this process.

    1. Thanks for the comment. I'm always glad to hear I get things right in these technical posts! Thankfully, Sinead doesn't have any more chemo appointments. She only needed the one blast, as her original surgery got the whole tumor. We only used the chemo for cleanup and to extend the margins. She should be all set!

  2. Hi, I know you posted this awhile ago but just came upon it. My Boston has had 4 mast cell tumors removed, all with clear margins and low grade so no further treatment was given after the surgical removals. Also, my vet put him on a regimen of daily Claritin 15mg/day. Maybe we could connect on Facebook and share what we know about mast cells and treatments since the information available is so sparse. Thanks for posting! If your on Facebook my name is Michelle Mccrackin please message me if you're interested in swapping info about our Boston and the mast cell info. Thanks!!